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. mwzw J. H. BELL. TELEGRAPH SYSTEM. APPLICATION men DEC. 27. I918- Patenfced June 10, 1 919.

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John /7( Lie UNITED STATES PATENT ornron JOHN H. BELL, OF SOUTH ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEGRAPH SYSTEM.

To all whom it may concern:

Be it known that I, JOHN H. BELL, a citizen of the UnitedStates, residing at South Orange, in the county of Essex, State of New Jersey, have invented certain new and useful Improvements in Telegraph Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telegraph systems and more particularly to duplex or similarly balanced electrical circuits.

The principal object of this inventionis to provide an improved organization of apparatus for indicating variation'o-f electrical characteristics in the circuits of duplex telegraph systems or equipments-wherein it may be required to maintain predetermined conditions of electrical balance between a plu- 'rality of circuits.

In carrying out the present invention,

there is provided electroresp'onsive switch-- ing means, current indicating means, and retarded circuit control v means coordinated with duplex circuits in such a manner that any'unbalance of the circuits will be indieated before such error may develop'f sufliciently to interfere with regular signaling operations. v

This invention is illustrated diagrammatically in the accompanying drawing, in which, for the sake of clearness'only so much of a telegraphic or signaling equipment has been shown as will be necessary to a clear understanding of the invention.

Referring to the drawing, reference character 1 indicates a telegraph transmitter which may be of any well-known form of pole changer or multiplex distributer arrangement, while resistance units 2 and 3 serve as the ratio arms of a bridge duplex respectively formed through an artificial line AL and a main line L. For the reception-of signaling impulses which may originate at a distant station on the line L, a circuit is. provided through a slow operating relay 5 and a polar relay 7 it being understood that the contacts of the polar relay may be arranged to control a receiving sounder or other suitable devices on which an incoming message is to be reproduced. As well understood in connection with duplex circuits, changes of current polarity set up b the transmitter 1, althou h non-eflective 1n the local receiving circuit formed by the relays 5 and 7, due to a balanced condi- Specification of Letters Patent.

Application filed December 27, 1918.

Patented J une 10, 1919. Serial No. 268,484.

tion of the artificial line AL and thereal lineL, will, however, control a suitable rece1v1n equipment at a distance station ,(not

shown on the line L. Conversely, impulsesor1ginating at such distant station will cause the operation of polar relay 7 Referring now more particularly to the 4 features of'the present invention, a resistance unit 10 which for convenience, should be of an adjustable type, is connected in a leak circuit which extends from the apex or outgoing connective point of the bridge duplex through the windings of two polar relays 11 and 15, to earth. Under the control of these polar relays is connected an ammeter 21 in-such a manner that,a current path maywhich an impulse is arriving from the line i L while an outgoing impulse is being trans- 15, as indicated by the conventlonal plus and minus signs in the drawing, close. contacts 12 and 16 respectively under the influence of an impulse of positive current from the transmitter 1, while a negative impulse from this transmitter will cause the'armatures of these relays to close contacts 13 and 17. Therefore, at the instant a negative impulse is sent from the transmitter 1, a circuit may be traced from the real line L by way of the contacts 6 of the'relay 5, the contacts 13 of the relay 11, thence through the operating windings .of the indicator orammeter 21, impedance 20 and the contacts 17 of the polar relay 15, to the artificial line.

The contacts of the relays 11 and 15 are so connected togetherand to ammeter 21 that any currents .from the'transmitter .1 which may stray between the real line L and the artificial line AL, due to inexactness of balance, will be so routed with respect to their direction through this meter mitted by the transmitter 1.. Relays 11 and I the needle may move either to the right. or to the left-hand side of acentral zero pomt. Therefore, when the nature of the unbalance is suchthat the artificial line is of higher impedance than the realdine, stray currents will flow from the artificial line to therea'l line and the needle 24 of the ammeter will accordingly be deflected in one direction, while for an inverse condition of'unbalance,

1 0 in which stray currentshave a tendency to flowjrom the real to'the artificial line, the needle of the ammeter will be deflected in the opposite direction. It will therefore be I clear that in addition to indicating the degree of unbalance, the ammeter. 21 will also indicate the direction of such unbalance,

thereby, definitely indicating the direction ofthe adjustment which should be made in the artificial line devices. 20., Referring more particularly to the pur pose of the relay5, this slow acting relay should vbe of such proportions or adjust-c .ment that although it will not'respondto incoming impulses from a distant station to. 25 separate itscontacts 6, it W111, however, re-

spond to what may be termed a steady current caused, for example, by an idle condition of the transmitting devices at a distant a station. Therefore, when'signaling impulses are coming in over the linelL, this relay will not operate. A prolonged impulse of steady current condition will, however, cause relay 5 to open its contact 6; By. this arrangement it will beclear' that the circuit of theammeter 21 is closed only when sig-,

may be changed to such point or points. that l v the needle 2 l will not be afiected but return to its zero position, thereby indicating" that the adjustments made have ,reestablisl 1ed a 5 0 balanced condition between the artlficlal line ALand the realline L.. Such adjustment of balance maybe carried ,outand all determinations relative thereto may bereached without in-any way interrupting or interfering with any messages (which may be under transmission over. the lineL.

' Long line circuits,.; particularly of the I open'wire type, are sub ect to variations in resistance andl'capacmy due ordmarilyto change in the weather as from dry to wet.

conditionsof the atmosphere, and in order to maintain a balanced condition of duplex circuits, it, is necessary for the telegra h attendants to vary the adjustment of t e de vices of the artificial line from time to time. The present arrangement provides that small or incipient variations of unbalance may be immediately indicated,'thereby per: mitting the necessary adjustments to be made in the artificial line before the degree of unbalance reaches a point at which the telegraphic originals would be interfered with, or before the unbalance condition causes entire failure of tlre telegraphicreceiving devices.

What is claimed is: a

1. In aduplex telegraph'system, a real line and an artificial l1ne, transmitting and receiving means included with said real and artificial lines, c urrent'indicatingfi lmeans,

pole changing means responsive to said transmitting means for controlling said current mdlcatlng means, and slow acting electroresponsive means. included with said.

receiving means'and controlling the connection of said current indicating means to said real and artificial lines.

2. In a duplex telegraph system, a real line and an artificial line, means included with said line for the reception of impulses incoming from said real line, transmitting means included with said lines for sending impulses over said real line, an ammeter, .a

slow actlng relay responsive tosaid ncom- 95 ing impulses, electroresponsive switching means for reversing connections' throu h said ammeter, and means. controlled by said slow acting relay to control the connection of said ammeter to said real and artificial lines. 1 1

line, an artificial line, "means for the recep tion of lmpulses from said real line, means I for the transmission of impulses to said real my name this 23rd ,day' of December A. 13.,-

line, current indicating means connected intermediate said real line and'said artificial line, pole changer means-controlled by said transmitter for controlling the, connections through said current indicating means, and o slow acting electroresponsive switching means included wit said real line. and said artificial line and responsivekto a prolonged 3. In a system of duplex circuits; a realimpulse from said'zreal lineto disable said u current'indicating'means; j, IIIWltIlGSS wher'eof,I hereunto subscribe .Jorm H. BELL, 

